diff --git a/src/blackmisc/aviation/aircraftsituation.cpp b/src/blackmisc/aviation/aircraftsituation.cpp
index 0c4985aa4..5844c086c 100644
--- a/src/blackmisc/aviation/aircraftsituation.cpp
+++ b/src/blackmisc/aviation/aircraftsituation.cpp
@@ -229,9 +229,15 @@ namespace BlackMisc
 
         void CAircraftSituation::setOnGroundFactor(double groundFactor)
         {
-            if (groundFactor < 0.0) { m_onGroundFactor = -1.0; return; }
-            if (groundFactor > 1.0) { m_onGroundFactor =  1.0; return; }
-            m_onGroundFactor = groundFactor;
+            double gf = groundFactor;
+            do
+            {
+                if (groundFactor < 0.0)   { gf = -1.0; break; }
+                if (groundFactor < 0.001) { gf =  0.0; break; }
+                if (groundFactor > 0.999) { gf =  1.0; break; }
+            }
+            while (false);
+            m_onGroundFactor = gf;
         }
 
         bool CAircraftSituation::guessOnGround(bool vtol, const PhysicalQuantities::CLength &cg)
@@ -271,6 +277,29 @@ namespace BlackMisc
             return CAircraftSituation::onGroundDetailsToString(this->getOnGroundDetails());
         }
 
+        bool CAircraftSituation::setOnGroundFromGroundFactorFromInterpolation(double threshold)
+        {
+            this->setOnGroundDetails(OnGroundByInterpolation);
+            if (this->getOnGroundFactor() < 0.0)
+            {
+                this->setOnGround(NotSet);
+                return false;
+            }
+
+            // set on ground but leave factor untouched
+            const bool og = this->getOnGroundFactor() > threshold; // 1.0 means on ground
+            m_onGround = og ? OnGround : NotOnGround;
+            return true;
+        }
+
+        bool CAircraftSituation::setOnGroundByUnderflowDetection(const CLength &cg)
+        {
+            IsOnGround og = this->isOnGroundByElevation(cg);
+            if (og == OnGroundSituationUnknown) { return false; }
+            this->setOnGround(og, OnGroundByElevationAndCG);
+            return true;
+        }
+
         QString CAircraftSituation::getOnGroundInfo() const
         {
             return this->onGroundAsString() % QLatin1Char(' ') % this->getOnDetailsAsString();
diff --git a/src/blackmisc/aviation/aircraftsituation.h b/src/blackmisc/aviation/aircraftsituation.h
index 275efe8e2..1cf134da8 100644
--- a/src/blackmisc/aviation/aircraftsituation.h
+++ b/src/blackmisc/aviation/aircraftsituation.h
@@ -188,6 +188,12 @@ namespace BlackMisc
             //! On ground details
             void setOnGroundDetails(CAircraftSituation::OnGroundDetails details) { m_onGroundDetails = static_cast<int>(details); }
 
+            //! Set on ground as interpolated from ground fatcor
+            bool setOnGroundFromGroundFactorFromInterpolation(double threshold = 0.5);
+
+            //! Set on ground by underflow detection, detects below ground scenarios
+            bool setOnGroundByUnderflowDetection(const PhysicalQuantities::CLength &cg);
+
             //! On ground info as string
             QString getOnGroundInfo() const;
 
diff --git a/src/blackmisc/simulation/simulatedaircraftlist.cpp b/src/blackmisc/simulation/simulatedaircraftlist.cpp
index c509ee5c9..7e5530029 100644
--- a/src/blackmisc/simulation/simulatedaircraftlist.cpp
+++ b/src/blackmisc/simulation/simulatedaircraftlist.cpp
@@ -108,6 +108,19 @@ namespace BlackMisc
             return c;
         }
 
+        int CSimulatedAircraftList::setFastPositionUpdates(const CCallsign &callsign, bool fastPositions, bool onlyFirst)
+        {
+            int c = 0;
+            for (CSimulatedAircraft &aircraft : (*this))
+            {
+                if (aircraft.getCallsign() != callsign) { continue; }
+                aircraft.setFastPositionUpdates(fastPositions);
+                c++;
+                if (onlyFirst) break;
+            }
+            return c;
+        }
+
         int CSimulatedAircraftList::setEnabled(const CCallsign &callsign, bool enabled, bool onlyFirst)
         {
             int c = 0;
@@ -134,7 +147,7 @@ namespace BlackMisc
             return c;
         }
 
-        int CSimulatedAircraftList::setAircraftParts(const CCallsign &callsign, const CAircraftParts &parts, bool onlyFirst)
+        int CSimulatedAircraftList::setAircraftPartsSynchronized(const CCallsign &callsign, const CAircraftParts &parts, bool onlyFirst)
         {
             int c = 0;
             for (CSimulatedAircraft &aircraft : (*this))
diff --git a/src/blackmisc/simulation/simulatedaircraftlist.h b/src/blackmisc/simulation/simulatedaircraftlist.h
index 4a3eb0268..c287753e4 100644
--- a/src/blackmisc/simulation/simulatedaircraftlist.h
+++ b/src/blackmisc/simulation/simulatedaircraftlist.h
@@ -79,13 +79,16 @@ namespace BlackMisc
             int setRendered(const Aviation::CCallsign &callsign, bool rendered, bool onlyFirst = true);
 
             //! Mark given callsign as enabled
-            int setEnabled(const Aviation::CCallsign &callsign, bool enabled, bool onlyFirst = true);
+            int setEnabled(const Aviation::CCallsign &callsign, bool enabled, bool onlyFirst);
+
+            //! Mark as fast position enabled
+            int setFastPositionUpdates(const Aviation::CCallsign &callsign, bool fastPositions, bool onlyFirst = true);
 
             //! Set model
             int setAircraftModel(const Aviation::CCallsign &callsign, const CAircraftModel &model, bool onlyFirst = true);
 
-            //! Set aircraft parts
-            int setAircraftParts(const Aviation::CCallsign &callsign, const Aviation::CAircraftParts &parts, bool onlyFirst = true);
+            //! Set aircraft parts and mark as synchronized
+            int setAircraftPartsSynchronized(const Aviation::CCallsign &callsign, const Aviation::CAircraftParts &parts, bool onlyFirst = true);
 
             //! Set aircraft parts
             int setAircraftSituation(const Aviation::CCallsign &callsign, const Aviation::CAircraftSituation &situation, bool onlyFirst = true);